Import of typography.html overrides any --paper-font-common-base mixin set.

[KeithHenry]

paper-input imports ../paper-styles/typography.html in three places:

paper-input/paper-input-container.html

Line 14 in 56089b9

<link rel="import" href="../paper-styles/typography.html">

paper-input/paper-input-error.html

Line 13 in 0a50e76

<link rel="import" href="../paper-styles/typography.html">

paper-input/paper-input-char-counter.html

Line 12 in 0a50e76

<link rel="import" href="../paper-styles/typography.html">

Each of these will cause any --paper-font-common-base mixin that is already set to be overridden with the typography.

Instead paper-input should not re-import typography.html, but it should include a comment similar to paper-radio-button's approach:

/*
This element applies the mixin `--paper-font-common-base` but does not import `paper-styles/typography.html`.
In order to apply the `Roboto` font to this element, make sure you've imported `paper-styles/typography.html`.
*/

See also this issue on paper-styles and this SO question.

[renfeng]

Paper elements should have consistency over --paper-font-common-base. I'd vote for paper-radio-button's approach as @KeithHenry suggested.